Year	Percent
1991	79.3
1992	79.23
1993	79.12
1994	78.98
1995	78.89
1996	78.85
1997	78.8
1998	78.73
1999	78.61
2000	78.5
2001	78.39
2002	78.23
2003	78.07
2004	77.9
2005	77.74
2006	77.71
2007	77.67
2008	77.62
2009	77.52
2010	77.51
2011	77.54
2012	77.6
2013	77.65
2014	77.71
2015	77.75
2016	77.72
2017	77.69
2018	77.66
2019	77.66
2020	76.6